Biodiversity net gain (BNG) is an approach to development that has the potential to be transformative in halting incremental biodiversity loss. Quite simply, the way of avoiding biodiversity loss that has been embedded in planning policy for many years has not worked.
Measures to avoid or minimise the impacts of development on biodiversity, restore affected areas and offset residual effects were designed to ensure no net loss. But for a number of reasons – not least the lack of monitoring and enforcement of proposed mitigation and compensation, uncertainties around effectiveness, and increasing fragmentation of habitats – the strategy has not been successful.
BNG is an alternative approach that could help halt incremental loss. It requires development projects to provide more habitat than is currently present on the site, adding more either on or, potentially, off site.
Calculating the baseline biodiversity value of a site, BNG accurately identifies the habitats present and factors in their condition and scarcity. From this the potential for net gain can be determined, after the mitigation hierarchy — which involves avoiding, minimising, mitigating then compensating for adverse impacts on biodiversity — has been applied.
In England, BNG will be mandated from 2023 if the Environment Bill is enacted this autumn. Developers will then be required to provide a minimum 10% net gain as part of receiving planning permission for a scheme, and that gain must be managed and maintained for a minimum of 30 years.
So that’s all great, isn’t it?
Well, yes it is. Any measure that helps us stop biodiversity loss and start to restore ecological networks is good news, especially as we become increasingly aware of the importance of the natural environment to societal well-being and economic prosperity. But it is only good news if it is implemented properly.
Successful provision of net gain requires policy and legislative alignment and responsibility across a number of government departments. Unfortunately we are not seeing as much of this as we expected, or need. For example, the ambition of the 25-year environment plan and the Environment Bill itself is at odds with the reforms proposed in the recent planning white paper and potential Planning Bill. Many of us were disappointed to see the contradictions between these.
And overarching these important policy areas is Project Speed, an initiative that emphasises the better, greener, faster provision of infrastructure but which, by its very name, suggests speed is the primary imperative. If government departments cannot ensure policy and legislation are properly aligned or cannot use consistent, robust language – readers may remember the term 'give regard to', which was too vague to be useful – then it undermines any sense of political will to see that BNG is properly implemented.
Ensuring net gain will also require competent ecologists, surveyors, planners and landscape architects as well as supporting services. The Chartered Institute of Ecology and Environmental Management (CIEEM) has been training ecologists and environmental managers in net gain and the biodiversity metric that underpins it for the past two years, but we know there are still skills gaps in our profession around competence to design BNG. For some other professions, it is a whole new ball game. We know from ongoing research that BNG is not well understood by some of the relevant professions, and time to do so is running out.
Of course, biodiversity net gain is not the only issue. Local nature recovery strategies, nature recovery networks, natural capital plans and environmental net gain are all current or proposed strategies.
If I were a planner, for example, my head would either be spinning or, more likely, stuck in the sand hoping someone would tell me what to do and when I need to do it. Yet planners need to know about all these initiatives, not only to ensure good outcomes but also to make strategic environmental provision in local plans and policies.
Competence is key. The application of the new biodiversity metric from the Department for Environment, Food and Rural Affairs (DEFRA) requires skills in habitat identification and accurate condition assessment. Misidentification or poor evaluation can significantly affect the baseline assessment from which the net gain is calculated.
Credible design and successful habitat restoration or creation can also require complex knowledge of soils, hydrology, management regimes and the effectiveness of habitat translocation. The complex debate between the advantages of providing the net gain on or off site also needs to be discussed.
Capacity is a further area of concern. We know from research carried out in 2013 and repeated recently that we already have insufficient ecologists and planners at local authorities to cover environmental issues across a number of policy and practice areas, and that biodiversity is being lost as a result. Now we are adding another area that is significant in terms of responsibility and workload.
If BNG is to be successfully integrated into the planning system, we need more capacity at local authorities, including supporting services such as local environmental records centres. The good news is that DEFRA has recognised the resource implications of mandating net gain, though it is still considering its response.
Guidance and templates will prevent each local planning authority having to reinvent the wheel. At CIEEM we have already produced practical principles and design report templates for BNG. This will mean that authorities do not end up receiving 50 different versions from 50 different developers, while developers will not have to use a different format for different councils. We need to ensure a consistent approach to make this less challenging.
Mechanisms are being developed to monitor ongoing provision of BNG, but this needs to happen apace so that local authorities do not have to develop their own mechanisms – unless they want to – but can use industry-standard approaches.
But we also need independent research into implementing mandatory net gain, so that we have a strong evidence base to identify and deal with areas of weakness. Again, this needs to be planned now rather than waiting until we face a problem.
Finally, standards matter: if BNG is to be done well, those providing it have to be accountable. A British Standard on net gain is due to be published imminently, although it is voluntary rather than mandatory.
There are a number of ways that the metric on which net gain is predicated can be misapplied or even manipulated to create a false baseline. Local planning authorities need to be confident that the information they are getting from developers and their ecologists or agents is sound, that the metric has been properly applied, and that the proposed biodiversity design is achievable.
There are building control processes to ensure that construction work is carried out to the right standard, so why not have something similar for biodiversity? Why not require those responsible for net gain to have demonstrated their competence to do so?
CIEMM is encouraged by the potential of BNG, but there is much work still to do to get the approach right and support all those involved in developing the confidence and competence they need. All stakeholders should be taking steps now to get the right systems, processes and resources in place to transform development work. The clock is ticking.
Dr Debadayita Raha and Prof. Sian Davies-Vollum 01 June 2023
Ben Willis 26 May 2023
Christopher Somorjay 19 May 2023